<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <!-- 适配手机端  -->
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>模块化</title>
</head>
<body>
    
   


    <button  id="btn">点我</button>
    
    <script src="index.js" type="module"></script>

   
</body>
</html>